I had a feeling it would probably be the 
Japanese post office paying the seller back. =/  
When a piece of registered mail coming from a 
friend of mine in Japan was "lost" that's what 
happened to me as well. And, just like you, the 
yen was down at it's lowest point in a very long 
time. =(

I'm a bit surprised over them saying they hoped 
it would happen again. I really wouldn't think 
it would take much to figure out who it was that 
did it.  Even if it is at a distribution center, 
the clerks who separate out the packages to send 
to the appropriate offices probably don't amount 
to more then a dozen - and not all of them are 
going to be working on a certain day.  Usually 
there are only certain people who handle the 
express / registered / certified mail. Of course 
I work at a smaller PO, not a distribution 
center so it's true workings might not be the 
same as the one I saw while training.

Small consolation, but these people who do this 
kind of thing almost always *do* get caught. And 
when they do, they serve time in a federal 
prison - no time off for good behaviour. :P  
It's such a shame to think of them opening the 
package, looking at what's inside and then 
tossing them though. O.o;  *sigh*